diff --git a/compiler/gen_wasm/src/wasm32_result.rs b/compiler/gen_wasm/src/wasm32_result.rs
index de0e939932..79d7f56596 100644
--- a/compiler/gen_wasm/src/wasm32_result.rs
+++ b/compiler/gen_wasm/src/wasm32_result.rs
@@ -186,7 +186,12 @@ wasm_result_primitive!(f64, f64_store, Align::Bytes8);
 wasm_result_stack_memory!(u128);
 wasm_result_stack_memory!(i128);
 wasm_result_stack_memory!(RocDec);
-wasm_result_stack_memory!(RocStr);
+
+impl Wasm32Result for RocStr {
+    fn build_wrapper_body(code_builder: &mut CodeBuilder, main_function_index: u32) {
+        build_wrapper_body_stack_memory(code_builder, main_function_index, 12)
+    }
+}
 
 impl<T: Wasm32Result + ReferenceCount> Wasm32Result for RocList<T> {
     fn build_wrapper_body(code_builder: &mut CodeBuilder, main_function_index: u32) {
diff --git a/compiler/gen_wasm/src/wasm32_sized.rs b/compiler/gen_wasm/src/wasm32_sized.rs
index f59b7fffd4..e7cfd7d9a0 100644
--- a/compiler/gen_wasm/src/wasm32_sized.rs
+++ b/compiler/gen_wasm/src/wasm32_sized.rs
@@ -31,12 +31,12 @@ impl Wasm32Sized for () {
 }
 
 impl Wasm32Sized for RocStr {
-    const SIZE_OF_WASM: usize = 8;
+    const SIZE_OF_WASM: usize = 12;
     const ALIGN_OF_WASM: usize = 4;
 }
 
 impl<T: Wasm32Sized + ReferenceCount> Wasm32Sized for RocList<T> {
-    const SIZE_OF_WASM: usize = 8;
+    const SIZE_OF_WASM: usize = 12;
     const ALIGN_OF_WASM: usize = 4;
 }
 
diff --git a/compiler/test_gen/src/wasm_str.rs b/compiler/test_gen/src/wasm_str.rs
index 91e208acb2..87020c7bd5 100644
--- a/compiler/test_gen/src/wasm_str.rs
+++ b/compiler/test_gen/src/wasm_str.rs
@@ -355,8 +355,8 @@ fn small_str_concat_small_to_big() {
 #[test]
 fn small_str_concat_small_to_small_staying_small() {
     assert_evals_to!(
-        r#"Str.concat "J" "JJJJJJJJJJJ""#,
-        [0x4a, 0x4a, 0x4a, 0x4a, 0x4a, 0x4a, 0x4a, 0x4a, 0x4a, 0x4a, 0x4a, 0x8b],
+        r#"Str.concat "0" "1234567890""#,
+        [0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x30, 0x8b],
         [u8; 12]
     );
 }